Colorants, colored articles and methods of making them

ABSTRACT

An article having a decorative visual surface appearance provided by a plastics composition which comprises a transparent or translucent plastics material having a colorant dispersed therein is characterised in that the colorant comprises a blend of discrete polymer particles substantially all of which have a minimum dimension in the range of 5 to 100 micron and a maximum dimension of no more than 10 mm, said particles being of a natural or synthetic organic polymer or a glass, the blend comprising particles of at least two distinct colors and/or shapes, and the plastics composition containing 0.1 to 8 percent by weight of the blend of polymer particles based on the weight of the plastics composition. The article can be made by a method which includes the steps of mixing together the blend and the plastics material or a precursor thereof and forming the article under conditions whereby the polymer particles in the colorant are not deformed to any substantial extent. The colored particles may be provided in a color concentrate homogeneously mixed with a polymer or precursor thereof or a wax. The articles may be moulded, cast, extruded, calendered or reinforced plastics articles, for example floor coverings.

CROSS-REFERENCE TO RELATED APPLICATIONS STATEMENT REGARDING FEDERALLYSPONSORED RESEARCH OR DEVELOPMENT

Not applicable

BACKGROUND OF THE INVENTION

This invention relates to colourants, including colourants forincorporation in plastics materials, to coloured articles made fromplastics materials which incorporate such colourants, and to methods ofmaking such colourants and articles.

Plastics articles made by moulding, casting, extrusion, calendering andsuchlike processes are well-known. Such articles may be thermoplastic orthermoset. It is often desirable that the surface of such plasticsarticles should have a decorative visual effect. Plastics materialswhich contain colourants such as dyes (i.e. coloured substancesdispersed at the molecular level) and/or pigments (i.e. colouredparticles up to about 1 micron in size) are well-known. Commonly, suchcolourants are uniformly dispersed throughout the plastics material, andthe plastics material and articles made therefrom are uniformlycoloured. Pigment particles scatter light as a consequence of theirsmall size, and as a result pigmented plastics materials are generallyopaque. Pure plastics materials are often transparent and remaintransparent when dyed. Inert fillers can be included in such dyedmaterials to provide translucency or opacity. The visual appearance ofthe surface of such dyed or pigmented plastics materials is generallyflat and lacking in depth and texture.

Plastics materials which incorporate particles of visual size (forexample, having a minimum dimension of about 5 micron) dispersedtherein, for example fibres, flakes or grits (spherical, roughlyspherical, or more or less irregular particles), are known. Fibres maybe incorporated in a plastics matrix to provide mechanicalreinforcement. Grits may be incorporated in a plastics matrix to provideabrasion resistance. If the colour of such particles differs from thatof the plastics matrix in which they are incorporated, such plasticsmaterials may have a speckled or mottled appearance, and such particleshave on occasion been incorporated for the purpose of providing adecorative surface effect.

BRIEF SUMMARY OF THE INVENTION

The invention provides an article having a decorative visual surfaceappearance provided by a plastics composition which comprises atransparent or translucent plastics material having a colourantdispersed therein, characterised in that the colourant comprises a blendof discrete polymer particles substantially all of which have a minimumdimension in the range 5 to 100 micron and a maximum dimension of nomore than 10 mm, said particles being of a natural or synthetic organicpolymer or a glass, the blend comprising particles of at least twodistinct colours and/or shapes, and the plastics composition containing0.1 to 8 per cent by weight of the blend of polymer particles based onthe weight of the plastics composition.

It will readily be understood that the term “substantially all” issynonymous with “largely or wholly” or “a substantial majority”. Forexample at least 90 or at least 95 or 100 percent of the particles maybe of the specified dimensions.

It will be appreciated that the decorative appearance of the articles ofthe invention is provided by the colourant within the plasticscomposition and is independent of any feature of shape or form of thearticle. The surface of such articles may be smooth, patterned orshaped, but is solid and continuous. It will further be appreciated thatthe portion of the article which incorporates the colourant may beoverlaid by a transparent or translucent layer through which thecoloured plastics composition can be seen.

The invention further provides a method of making a plastics articleincluding the steps of:

(a) mixing together (i) a colourant which comprises a blend of discretepolymer particles substantially all of which have a minimum dimension inthe range 5 to 100 micron and a maximum dimension of no more than 10 mm,said blend comprising particles of at least two distinct colours and/orshapes, and (ii) a transparent or translucent plastics material or aprecursor thereof, and

(b) forming said article under conditions whereby said polymer particlesare not permanently deformed to any substantial extent.

The invention further provides a colourant in the form of a colourconcentrate which comprises discrete coloured particles homogeneouslymixed with a polymer or precursor thereof or a wax, characterised inthat substantially all of the particles are polymer particles which havea minimum dimension in the range 5 to 100 micron and a maximum dimensionof no more than 10 mm, which polymer particles are of at least twodistinct colours and/or shapes. The colourant-of the invention may takethe form of a masterbatch material wherein the coloured particles arehomogeneously mixed with a thermoplastic resin binder.

The decorate surface layer of a plastics article according to theinvention has an unusual and attractive dappled appearance withremarkable visual depth and texture. The article surprisingly has thisappearance even when, as is desirable, the colourant is well mixed withthe plastics material so that it is uniformly dispersed therein. Such adecorative surface layer may if desired be designed to mimic naturalmaterials, for example various types of stone or rock, includingsedimentary, igneous and in particular metamorphic rock such as slate.Other examples of such natural materials include leather and wood.

The polymer particles in the colourant may take the form of fibres,flakes, spheroids or grits or mixtures thereof. It may be preferred thatsubstantially all the polymer particles have a maximum dimension in therange 0.5 to 10 mm. Preferred fibres may have a titre in the range 1 to30 decitex, often 1 to 6 decitex, and a length in the range 0.5 to 10 mmor 0.1 or 0.25 to 10 mm. Such fibres are commonly referred to as staplefibres and may also be referred to as flock, particularly when they havea length below about 5 mm. Fibre flock may be prepared by cutting longerfibres to lengths of about 0.25 mm or above. Shorter flock may beprepared by grinding, for example cryogenic grinding. Preferred flakesmay have a basis weight in the range 10 to 50 grams per square meter inthe plane of the flake and maximum dimensions in the range 0.5 to 5 mmor 0.1 or 0.25 to 5 mm. Suitable flakes may be prepared for example bychopping or grinding shredding (including cryogenically grinding) apolymer film. Preferred spheroids include polymer beads and glass beads.It will be appreciated that the particles should desirably be of a shapeand composition such that they do not damage the processing equipment,for example by abrasion. Accordingly, the use of glass powder or flakemay generally be less favoured, as compared with glass fibre and beads,in extrusion and suchlike techniques.

The particles may consist essentially of a natural organic polymer, asynthetic organic polymer or glass. They may consist essentially of anatural polymer which has been processed, for example they may consistessentially of cellulose in the form of regenerated viscose. Use ofsynthetic organic polymers or processed natural organic polymers may bepreferred. Use of glass particles may alternatively be preferred in someapplications. Examples of suitable types of glass include A-, C-, E- andS-glass. Each polymer particle usually contains a single type of polymerbut may contain a mixture of more than one type of polymer. Theparticles within the blend may consist of the same or different types ofpolymer or polymer mixture. The material of the polymer particles shouldbe chosen having regard to compatibility between this material and theplastics material in which the particles are to be incorporated. Aspecific type of polymer particle is unplasticised cellulose film,optionally pigmented, for example regenerated cellulose film such asthat made by the viscose process, which has been reduced to thespecified size and optionally dyed.

The polymer particles are preferably both mechanically and thermallystable under the temperatures encountered during processing, inparticular plastics processing, so that they substantially retain theiroriginal shape and do not degrade during such processing. Deformation ofthe particles during processing may give rise to a streaky appearance ina plastics article made thereby. The decorative visual surfaceappearance of the article of the invention may have an isotropicappearance. The polymer particles remain individual and discrete duringprocessing and in the plastics article. The polymer may be athermoplastic polymer, in which case it will be understood that theprocessing temperature should be chosen to avoid undesirable deformationof the particles. It has been found that certain thermoplastic polymers,particularly semi-crystalline polymers, may be processed at above theirglass transition temperatures without the occurrence of suchdeformation. Other thermoplastic polymers, particularly amorphouspolymers, are preferably processed below their glass transitiontemperatures. The polymer may be crosslinked and may be thermoset. Thepolymer may be a polymer which has inherent mechanical stability attemperatures up to the decomposition temperature of the polymer, thisdecomposition temperature being above the processing temperature of theplastics material. For example, the polymer may be cellulose,particularly regenerated viscose, or an acrylonitrile polymer orcopolymer, particularly a copolymer containing at least 85 percent byweight acrylonitrile units. Alternative types of organic polymer whichmay be used in some applications include polyamides, for example 6:6 and4:6 polyamides, and polyesters.

The polymer particles are pigmented or dyed to selected colours.Pigments scatter light, and therefore the presence of pigmented polymerparticles may reduce the visual depth of the decorative surface layer inan article according to the invention. The blend of polymer particlesmay include a small proportion of white and/or black pigmentedparticles, for example matt pigmented fibres, in addition to theparticles of distinct colours. Polymers which can readily be dyed to awide range of intense colours, in particular cellulose and acrylonitrilecopolymers, are preferred. Organic polymer particles are available in awide and precisely controllable range of intense colours, and this is anadvantage of the invention. The polymer particles may be pigmented ordyed during their manufacture or may be dyed subsequent to theirmanufacture. Glass particles are available in a range of colours. Thecoloured polymer particles preferably exhibit good light fastness.

The polymer particles contained in the colourant blend preferablyexhibit a small number of distinct colours, more preferably no more thanabout twelve, further preferably no more than about six, distinctcolours. This allows the production of colourants in a wide range ofshades (colours) by appropriate blending of polymer particles from asmall range of distinct colours. This leads to simplicity inmanufacture, reproducibility and stock control. The term “distinctcolours” as used herein means colours of markedly differing hue, that isto say wide radial spacing within a conventional hue circle or colourwheel. Black and white are not considered to be “colours” in the contextof the present invention, and accordingly black and/or white particles,if present, are additional to the particles of distinct colours in thecolourant.

The blend preferably includes polymer particles of at least two intensecolours optionally together with black and/or white particles. The term‘intense colour’ as used herein means an intense (saturated) colourpreferably located towards the circumference of a conventional huecircle or colour wheel. The at least two intense colours are preferablychosen so that they are widely spaced in such a hue circle. Thus amixture of various shades of red such as crimson, vermillion, ruby,claret, cherry, carnation and scarlet is not considered to consist ofdistinct colours in the context of the invention even though they can bedistinguished by the naked eye, and even if such colours are intensecolours. The points representing the intense colours define a polygonalarea within the hue circle, the polygonal area being triangular if threeintense colours are used. The colourant of the invention may be preparedin essentially any shade within this polygonal area by blending thepolymer particles of the chosen intense colours in suitable proportions.The lightness within a conventional colour cylinder of the colourant ofthe invention may be varied by altering the proportion of black and/orwhite particles in the blend. The intense colours may be selected fromthe group consisting of the primary colours red, yellow and blue. As maybe particularly preferred, the intense colours may alternatively beselected from the group consisting of the colours magenta, cyan andyellow, because it has been found that a wide range of shades isachievable using the colours in this group. The blend may comprisepolymer particles of more than three intense colours, preferably no morethan six intense colours, optionally together with black and/or whiteparticles. This allows the production of a wider range of shades than ifonly three intense colours are used, because the size of the polygonalarea is increased. This also provides flexibility in manufacture,because many shades within the polygonal area can be obtained in morethan one way.

A desired shade can be matched by experimental mixing of the polymerparticles. It will be understood that the perceived shade of a colourantmay differ when viewed on its own and after incorporation in an article.It has generally been found that the perceived shade of a plasticsarticle according to the invention is not necessarily predictable fromthe colours of the polymer particles by classical colour-mixingtheories.

The colours of the polymer particles may be chosen to avoid metamericeffects.

The polymer particles contained in the blend may alternatively be of asingle colour but of different shapes. For example, the blend mayconsist of a mixture of fibres and flakes of the same or similarcolours. Decorative articles containing such a colourant have a visuallyattractive appearance different from that of a pigmented article or anarticle containing only particles all of which are of similar shape.

The blend of polymer particles may additionally compromise colourlesspolymer particles. This may be advantageous in that it permits theformulation of the colourants of the invention in a wide range ofshades, all of which are designed to be incorporated in plasticsmaterials in the same proportions. This leads to simple procedures inthe manufacture of the plastics articles of the invention and enablesreliable blending of two or more colourants to provide intermediatecolours if desired. Such colourless particles may suitably be of thesame polymer or polymers as may be used for the coloured particles.Examples of such colourless particles include organic fibres such asviscose and acrylic fibres and glass fibres which contain neither dyenor pigment.

The colourant may additionally comprise small proportions of one or moreconventional pigments. Pigments scatter light and therefore if theproportion of pigment is too high the advantageous visual texture anddepth provided by the invention may be lost. The proportion of pigmentis often preferably no more than about 5 percent by weight based on theweight of the polymer particles, including any pigment present in thepolymer particles, although higher proportions, for example in the range5 to 10 percent, may be desirable in some applications. Addition ofpigment may be used to vary the lightness of colour, the coloursaturation and the visual texture and depth of the decorative surface ofan article incorporating the colourant. A preferred type of pigment is awhite pigment such as titanium dioxide. The plastics composition mayadditionally comprise small proportions of conventional dyes.

The colourant may additionally comprise other particulate materialswhich provide specific visual effects when incorporated in a plasticsarticle, for example mica flakes, quartz particles, short-cut carbonfibres, opalescent, pearlescent and fluorescent pigments, and metallicpigments.

The colourant of the invention may comprise a, generally thermoplastic,resin binder which serves to bind the polymer particles together, forexample in the form of paste or masterbatch granules or pellets. Suchpaste, granules or pellets are often more convenient to handle, forexample during storage, transport and weighing, than blends of the freepolymer particles. The binder is preferably readily miscible with theplastics material in which the colourant of the invention is dispersedduring plastics processing to form a plastics article. This allowsuniform dispersion of the polymer particles throughout the plasticsmaterial to be readily achieved. Examples of binders known generallyfrom masterbatch technology include low density polyethylene,ethylene/vinyl acetate copolymers and mineral waxes. Thus, the particleswill be dispersed in a polymer or precursor thereof or a wax. The paste,granules or pellets may contain up to about 60 percent by weight polymerparticles, often 20 to 60 or 40 to 60 percent by weight. The granules orpellets may additionally comprise small amounts of conventional dyesand/or pigments. These colourants of the invention are useful in theplastics industry and can be subsequently utilised by conventionalmasterbatch dosing or addition techniques.

The decorative plastics composition in the article aspect of theinvention preferably contains 1 to 5 percent by weight of the blend ofpolymer particles, based on the total weight of the plastics compositionincluding the plastics material. The depth of colour, colour saturationand visual texture of the decorative surface may be varied by alteringthe concentration of coloured particles and pigment in the material ofwhich it is composed. It has generally been observed that the viscosityof such a composition increases as the concentration of polymerparticles is increased. It has also been observed that directionalvisual effects may be produced in extruded, calendered and suchlikearticles as the concentration of polymer particles is increased. It hasfurther been observed that directional effects can be enhanced if thepolymer particle blend contains particles of high aspect ratio, forexample 20-30 decitex flat fibres, particularly if such particles aredark in colour, for example black.

The polymer particles are preferably uniformly dispersed throughout theplastics material. This can be accomplished by known plastics processingtechniques. It may be desirable to treat or coat the particles, forexample by applying a suitable finish, to ensure good dispersion andavoid clumping. In the method of the invention the polymer particles maybe mixed with a thermoplastic polymer. Alternatively, the particles maybe mixed with a polymer precursor, for example a thermoplastic orthermosetting polymer resin, which is subsequently cured to form apolymer.

The plastics material used in the articles of the invention may betranslucent or preferably transparent. The refractive index of thepolymer particles may be matched more or less closely to that of theplastics material to reduce light scattering. A translucent plasticsmaterial may contain a filler, for example it may contain up to about 30or 50 percent by weight filler based on the total weight of thecomposition. Such a filler is generally a material, often of relativelysmall particle size, with refractive index comparable to that of theplastics material. The plastics material preferably contains no pigmentor low levels of pigment. A preferred maximum level of pigment(including any pigment in the polymer particles) is 0.1 percent byweight based on the total weight of the plastics composition, althoughhigher levels, for example 0.2 or 0.3 percent or in the range 0.2 to 0.5percent, may be used in some applications.

Examples of articles of the invention include moulded, cast, extrudedand calendered articles. Moulded articles include injection mouldedinternal and external automotive, aeronautic and marine components,panels, trims, catering ware, houseware such as hair dryers, electrickettles, irons, blenders and mixers, refrigerator and freezercomponents, vacuum cleaners, floor polishers, brushes, buckets andbowls, cutlery handles, storage containers, picnic ware, suitcases,coathangers, garden furniture, garden tools, wheelbarrows, planters,toys, telephones and suchlike articles. Moulded articles further includevacuum formed articles such as include containers, for example for foodand drink, lubricating oil and detergents. Compression moulded articlesinclude electrical plugs and sockets, toilet seats, picnic ware andtableware. Extruded and calendered articles include sheets, films andfoils, vinyl upholstery, stationery goods, synthetic security paper,credit cards, floor coverings, including resilient floor coverings, inparticular vinyl floor coverings, wall coverings, blinds and awnings,particle board surfacing and extruded profiles. Cast articles includesurfboards, boat hulls, service counters and claddings.

The invention also provides a reinforced plastics article comprisingreinforcing fibres dispersed in a polymer matrix, the fibres having aminimum dimension (diameter) in the range 5 to 100 micron and a maximumdimension (length) of no more than 10 mm, characterised in that eitherthe reinforcing fibres comprise fibres of two or more distinct coloursor the reinforcing fibres comprise fibres of a first colour and thearticle additionally comprises flake particles of a second colourdistinct therefrom, the flake particles having a minimum dimension inthe range 5 to 100 micron and a maximum dimension of no more than 10 mm.The reinforcing fibres are preferably of glass, although other types offibres may also be used. The polymer matrix may be thermoplastic orthermoset. The article generally contains about 10 to 50, preferably 20to 40, percent by weight reinforcing fibres based on the weight of thearticle. The article may contain a blend of coloured and uncolouredfibres, in which case it may be preferred that the article contain 0.1to 8 percent by weight coloured fibres and optional flakes. The colouredreinforcing fibres and optional flakes are preferably of no more thanabout six distinct colours.

DETAILED DESCRIPTION

The invention is illustrated by the following Examples, in which allparts and proportions are by weight unless otherwise specified:

EXAMPLE 1

Various blends of polymer particles of distinct colours were prepared.The polymer particles used were 3.3 decitex viscose rayon nominal 0.5 mmflock fibre dyed with reactive dyes to intense magenta, cyan, yellow andblack shades and regenerated viscose film of basis weight 35 grams persquare meter ground into small particles and dyed black. The blendsadditionally contained between 0 and 20% uncoloured fibre and/or groundfilm.

A PVC composition consisting of 100 parts PVC resin, 26 parts diisooctylphthalate, 5 parts epoxidised soya bean oil and 2 parts stabiliser wasmixed as powder. 2.5% by weight on the weight of this composition of oneof the blends of coloured polymer particles was added and thoroughlymixed into the composition. The PVC composition was fluxed on a 2-rollmill at 160° C. for 5 minutes and extruded between bead-blasted aluminumor siliconised paper at 158° C. and 5515 kPa (800 psi) to form a sheetuniformly 0.1-2 mm, typically 1 mm, thick. The coloured sheets had anattractive dappled and speckled appearance, and were suitable for use asresilient floor coverings.

EXAMPLE 2

Blends of polymer particles were prepared as in Example 1, except thatthey contained about 3 to 6% mica. A cast was taken from a piece ofnatural unpolished slate and used to form a mould. 100 parts ofconventional polyester moulding resin was thoroughly mixed with 3.5parts polymer particle blend and the mixture poured into the mould. Theresin was cured and the cured article removed from the mould. It had adecorative appearance closely resembling that of natural slate.

EXAMPLE 3

Blends of polymer particles were prepared as described in Example 1.Each blend was thoroughly mixed into a commercial polyester castingresin (3.5 parts polymer particle blend in 100 parts composition)together with a small amount of titanium dioxide dispersion. The resinwas cast to form sheets about 3 mm thick. The percentage compositions ofthe polymer particle blends and the general colour of the sheets areshown in Table 1:

TABLE 1 Yellow Magenta Cyan Black Undyed Black Undyed Total Dyed Ref.Fibre Fibre Fibre Fibre Fibre Film Film Mica Particles Colour C21A 19.95.1 16.4 30.1 14.4 14.0 55.9 Grey Green C22A 14.4 56.8 28.8 43.2 Midgrey C24H 56.0 15.0 21.5 7.5 92.5 Greyish pink C25A 47.6 23.6 28.8 100.0Pink C26B 28.8 6.8 6.8 28.8 28.8 71.2 Greenish grey C31E 62.8 8.5 14.314.3 85.7 Yellowish brown C34A 3.4 68.5 3.4 24.7 6.8 Light grey C35A13.0 2.7 3.4 52.4 3.4 25.0 22.6 Reddish grey C37A 12.7 6.8 3.4 48.6 3.425.0 26.4 Light pink C38E 19.9 2.7 3.4 45.4 3.4 25.1 29.5 Pale greenishyellow E28C 9.9 61.4 28.7 100.0 Dark grey E29B 24.7 3.4 42.8 0.3 28.899.7 Dark greenish grey E33B 42.8 12.0 16.4 28.8 100.0 Dark grey E43E16.9 2.9 0.9 1.1 14.0 64.3 21.7 Light sandstone E43G 50.0 8.6 2.1 3.635.7 64.3 Dark sandstone H42Q 47.4 23.7 14.3 14.3 0.3 99.7 Red slateH42R 21.4 21.4 28.6 28.6 71.4 Green slate H42T 20.0 8.6 42.9 28.6 100.0Black slate

The amount of titanium dioxide dispersion in 100 parts composition was0.5 part in the ‘C’ series of samples, 0.25 part in the ‘E’ series and0.06 part in the ‘H’ series.

The sheets had a speckled appearance due to the inclusion of blackground film. Using a magnifying glass, it was possible to see theindividual coloured fibres in the sheets. To the naked eye, the sheetshad a visually attractive dappled appearance and texture in which theindividual fibres and their colours could not easily be discerned.

Cast were taken from natural pieces of sandstone and slate and used asmoulds. Resins containing polymer particle blends shown in Table 1having a sandstone and slate appearance were then cast in the moulds.The coloured castings had a visual appearance closely resembling that ofthe natural pieces of stone and could not easily be distinguished fromthem without close examination.

EXAMPLE 4

PVC sheets were prepared by the method of Example 2 using the followingrecipes, in which the fibre/film blends are those identified in Table 1by the given reference codes:

Light sandstone (York stone) Plasticised PVC resin 82.6 Fibre/film blend(E43E) 1.9 Titanium dioxide 0.083 Dark sandstone Plasticised PVC resin80.9 Fibre/film blend (E43G) 2.92 Titanium dioxide 0.12

The sheets closely resembled the types of stone named in the recipes andwere suitable for use in resilient floor coverings.

EXAMPLE 5

Masterbatch pellets were prepared by twin-screw compounding atapproximately 200° C. (a) 40 parts viscose fibre flock and choppedviscose film (flake) as colourants with (b) 60 parts low-densitypolyethylene (LDPE) as carrier resin. Dyed flock and flake were used ascolourants and were dried at 80° C. before use. The carrier resin hadmelt flow index 20 g/10 min at 190° C. under 2.16 kg load, measuredaccording to 50 1133 and cond 4/ASMT D 12358, method B, cond E. Thepellets contained flock and flake in the following proportions:

Reference E33 E79 Yellow fibre 1.28 0.60 Magenta fibre 0.36 0.38 Cyanfibre 0.00 1.55 Black fibre 0.50 0.28 Ecru (unpigmented, undyed) fibre0.00 0.19 Black flake 0.86 0.00

Masterbatch pellets containing 10% titanium dioxide dispersed in LDPE ascarrier resin were also prepared. It was found advantageous to dry theviscose-containing masterbatch pellets in an oven before moulding toavoid surface watermarking in the moulded articles.

Specimen bars were prepared by injection moulding blends of thesemasterbatch pellets with polypropylene and ABS as let-down resins. Themaximum proportion of the viscose-containing masterbatch pellets in theblend was 7.5% (corresponding to 3% of fibre and flake in the blend) andof the pigment-containing resin was 1% (corresponding to 0.1% of pigmentin the blend). The samples had a visually attractive dappled appearancewhich was of considerable visual depth. This visual depth was moreevident for those samples containing lower proportions of the pigment.The E33-containing samples were grey and the E79-containing samplesbluish-green in colour.

Kettle lids were made by injection moulding using the same masterbatchpellets and let-down resins. Polypropylene was moulded using melttemperature 220° C., mould temperature 40-45° C., injection speed 60mm/sec, injection pressure 1600 bar, holding pressure 30 or 150 bar,holding pressure time 9 sec, cooling time 30 sec and cycle time 55 sec.The blends used for moulding contained 7.5% E33 or E79 pellets and 1 or2% pigmented pellets. ABS was moulded using melt temperature 250° C.,mould temperature in the range 45-75° C., injection speed 90 mm/sec,injection pressure 1600 bar, holding pressure 200 bar, holding pressuretime 9 sec, cooling time 30 sec and cycle time 61 sec. The blends usedfor moulding contained 7.5% E79 pellets and 1% pigment pellets, or 7.5or 15% E33 pellets and no pigment pellets. The moulded productreproduced the detail in the mould well, including smooth areas,patterned areas and surface lettering.

Utility containers for holding desktop articles and stationery were madeby injection moulding with hot runner tooling, using the samemasterbatch pellets and polystyrene resin as let-down resin. Mouldingwas carried out using melt temperature 229 or 239° C., barreltemperature 210 or 220° C., mould temperature 40° C., injection speed 17or 35 mm/sec, injection pressure 392 bar, holding pressure 40 or 50 bar,holding pressure time 10 sec, cooling time 25 sec and cycle time 44 sec.The blends used for moulding contained 7.5% of E33 or E79 pellets and0,1 or 2% of pigmented pellets.

What is claimed is:
 1. An article provided by a plastics compositionwhich comprises a transparent or translucent thermoplastics materialhaving a colorant uniformly dispersed therein characterized in that thecolorant comprises a blend of discrete particles at least 90% of whichhave a minimum dimension which is from 5 to 100 μm and a maximumdimension of no more than 0.5 mm, said particles being of a natural orsynthetic crosslinked thermoplastic organic polymer which is compatiblewith the thermoplastics material such that the surface of the article issmooth and said particles being mechanically and thermally stable suchthat they did not degrade during processing that created the article,the blend comprising particles having at least two distinct colors, notblack and not white, and the plastics composition containing 0.1 to 8percent by weight of the blend of said polymer particles based on theweight of the plastics composition.
 2. An article according to claim 1,characterized in that the plastics composition contains 1 to 5 percentby weight of the blend of the particles based on the weight of theplastics composition.
 3. An article according to claim 1, characterizedin the plastics composition contains no more than 0.1 percent by weightof pigment based on the weight of the plastics composition.
 4. Anarticle according to claim 1, characterized in that the plasticscomposition contains no more than 5 percent by weight of pigment basedon the weight of the blend of the particles.
 5. An article according toclaim 1, characterized in that at least some of the particles arespheroids.
 6. An article according to claim 1, characterized in that atleast some of the particles are fibres.
 7. An article according to claim1, characterized in that at least some of the particles are flakes. 8.An article according to claim 1, characterized in that the blendcontains particles of no more than about six distinct colors.
 9. Anarticle according to claim 1, characterized in that the blend comprisesparticles of at least three intense colors, optionally together withblack and/or white particles.
 10. An article according to claim 9,characterized in that the blend comprises particles of no more than sixintense colors, optionally together with black and/or white particles.11. An article according to claim 1, characterized in that the blendcomprises colored particles and colorless particles.
 12. An articleaccording to claim 1, characterized in that it is a moulded, cast,extruded or calendered plastics article.
 13. An article according toclaim 1, wherein at least some of the particles are irregular shapedparticles.
 14. A method of making an article according to claim 1,characterized in that it includes the steps of: (a) mixing together (i)colorant which comprises a blend of discrete particles at least 90% ofwhich have a minimum dimension which is from 5 to 100 μm, and a maximumdimension of no more than 0.5 mm, said particles being of a natural orsynthetic cross-linked thermoplastic organic polymer, said blendcomprising particles of at least two distinct colors, not black and notwhite, and (ii) a transparent or translucent thermoplastics rial or aprecursor thereof, said particles being present in an amount from 0.1 to8 percent by weight of the mixture, so that the particles are compatiblewith and are uniformly dispersed in the thermoplastics material, and theparticles are mechanically and thermally stable such that they do notdegrade during formation of the article; and (b) forming the articleunder conditions whereby the particles in the colorants are not deformedto any substantial extent.